1. Field of the Invention
The present invention relates generally to an oil pan for an internal combustion engine. Specifically, the present invention relates to an oil pan which is easily manufactured and which exhibits low noise emmission characteristics.
2. Description of the Prior Art
Various designs have been proposed for oil pans of internal combustion engines. Generally, the oil pan is positioned at a lower side of a cylinder block of an internal combustion engine and is of a comparatively deep relief for receiving accumulated lubricating oil from the engine block which is pumped throughout the engine under pressure by an oil pump. Such oil pans are generally made by pressing of a thin metal plate. Consequently, when engine vibration is applied thereto a relatively loud noise may be caused by the vibration of the oil pan.
To address this problem, Japanese Utility Model application 54-25941 disclose an oil pan for an internal combustion engine having a two-ply construction. The disclosed oil pan includes an outer layer and an inner layer with a given gap therebetween, the inner layer being formed with a plurality of holes therethrough. Lubricating oil is allowed to flow between the inner and outer layers and the holes provided in the inner layer are effective to reduce vibration applied to the oil pan.
However, according to the above construction, since the inner layer must be formed with the plurality of holes and must be fixedly supported by the outer layer, manufacturing of the oil pan becomes complex and costs are raised significantly due to the number of parts and required processing. Further, since the oil flows between the outer and inner layer through the plurality of holes of the inner layer, oil flow caused by oil pan vibration is impeded and energy loss may be incurred. Also, the limits in constructing the oil pan limits the gap between the inner and outer layers, etc., and it is thus difficult to obtain sufficient noise reduction.
Thus it has been required to provide an oil pan for an internal combustion engine in which sufficient vibration reduction and noise emmission reduction can be obtained with simple, low cost construction.